On the theory side, the nature of the \(X(3872)\)  is still a controversial issue,
where different approaches have not reached yet a full agreement.
The analysis of Ref. [1]}, [2]}, [3]}, [4]} favors
a \(D^0\bar{D}^{*0}/\bar{D}^0D^{*0}\)  bound state,
as the \(X(3872)\)  mass is very close to the \(D^0\bar{D}^{*0}\)  threshold.
Other works describe the \(X(3872)\)  as
a \(D^0\bar{D}^{*0}/\bar{D}^0D^{*0}\)  virtual state [5]},
a tetraquark [6]} or a hybrid state [7]}.
On the other hand, it has also been considered as a mixture of a charmonium \(\chi _{c1}^{\prime }=\chi _{c1}(2P)\)  with a \(D^0\bar{D}^{*0}/\bar{D}^0D^{*0}\)  component [8]}, [9]}. The mixing can be induced by the coupled-channel effects, and the S-wave \(\chi _{c1}^{\prime }-D\bar{D}^{*}/\bar{D}D^{*}\)  coupling can also explain the closeness of \(m_{X(3872)}\)  to the threshold of \(D^0\bar{D}^{*0}\)  naturally [10]}, [11]}. Furthermore, the existence of the substantial \(\chi _{c1}^{\prime }\)  component in the \(X(3872)\)  state is supported by the analyses of the lager production rates of \(X(3872)\)  both in \(B\)  decays [8]}, [13]} and at hadron colliders [14]}.
